--> Abstract: Identification of Avulsion Stratigraphy Style as a Characterization Strategy for Predicting Channel-Body Connectivity in Fluvi; #90063 (2007)

Datapages, Inc.Print this page

Identification of Avulsion Stratigraphy Style as a Characterization Strategy for Predicting Channel-Body Connectivity in Fluvial Reservoirs

 

Jones, Heather L.1, Elizabeth A. Hajek1, Paul L. Heller1 (1) University of Wyoming, Laramie, WY

 

Ancient avulsion-dominated alluvial basins preserve thousands of manifestations of avulsions and these deposits constitute dominant reservoir intervals in fluvial basins. Six fluvial formations located in the western United States (Wyoming, Colorado and Utah) have been identified as avulsion-dominated. Measured stratigraphic sections and detailed core descriptions were used to characterize avulsion stratigraphy throughout a fluvial formation and then compared to well log data where available. Data were collected on a basin-wide scale for each fluvial formation in order to document the spatial distribution of preserved avulsion stratigraphy. Two categories of avulsion stratigraphy have been recognized in outcrop, core and well logs. An avulsed channel that is underlain by silt to fine-grained crevasse splay deposits is categorized as foreshadowed avulsion stratigraphy. This scenario produces greater lateral and vertical sand body connectivity through the preservation of laterally extensive crevasse splay deposits. Stratigraphically abrupt avulsion stratigraphy is recognized by the direct juxtaposition of the avulsed channel atop very fine-grained (clay to silt) floodplain material. This scenario results in channel sand bodies that are isolated and compartmentalized by floodplain material, which can act as a seal inhibiting channel-body connectivity. The results from the research demonstrate that each fluvial formation has preserved a dominance of either foreshadowed or stratigraphically abrupt avulsion stratigraphy basin wide. This suggests that recognition of avulsion stratigraphy in a fluvial reservoir during the exploration stage is a helpful tool for understanding the subsurface expression of channel sand bodies and their connectivity.

 

AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California